Circular magnetic domain devices

Claim 2

A circular magnetic domain device including a layer of uniaxial magnetic material having a single unique, easy magnetisation direction substantially normal to a major surface thereof; generation means for generating circular magnetic domains within the said layer; propagation means for causing the circular magnetic domains to propagate along at least one path in the said layer; and detection means for detecting the propagating domains by causing a generated wave to follow a path in the said layer which intercepts at least one domain propagation path and to thEreby cause the propagating domains to interact with the generated wave.

Claim 3

A circular magnetic domain device as claimed in claim 1 wherein the detection means include a generating transducer associated with the said layer for generating the said wave, the generated wave following a path which intercepts at least one domain propagation path; and a detection transducer for detecting the wave after it intercepts the said at least one domain propagation path.

Claim 4

A circular magnetic domain device as claimed in claim 2 wherein the combined effects of the field distribution near to, and within the propagating circular magnetic domains and the domain stabilising field are arranged to inhibit a conversion from one type of wave to another type of wave, and wherein the detection transducer is adapted to detect acoustic waves, magnetoacoustic waves and magnetic waves, the wave type detected indicating the presence or absence of a circular magnetic domain.

Claim 5

A circular magnetic domain device as claimed in claim 2 wherein the generating transducer is adapted to generate magnetic waves in the said layer and wherein the detection transducer is adapted to detect the magnetic waves and any changes therein.

Claim 6

A circular magnetic domain device as claimed in claim 2 wherein the generating transducer is adapted to generate acoustic waves in the said layer, the combined effects of the field distribution near to, and within the propagating circular magnetic domains and the domain stabilising bias field being arranged to convert the acoustic waves into magnetic waves before the waves intercept the said at least one domain propagation path, wherein the magnetic waves, after propagation path interception, revert to magnetoacoustic waves and then substantially wholly to acoustic waves, and wherein the detection transducer, depending on its position relative to the point of path interception, is adapted to detect either magnetic waves, magnetoacoustic waves or acoustic waves.

Claim 7

A circular magnetic domain device as claimed in claim 2 wherein the generating transducer is adapted to generate acoustic waves in the said layer, and wherein the detection transducer is adapted to detect the acoustic waves and any changes therein.

Claim 8

A circular magnetic domain device as claimed in claim 2 wherein the combined effects of the field distribution near to, and within the propagating circular magnetic domains and the domain stabilising field are arranged to promote a conversion from one type of wave to another type of wave, and wherein the detection transducer is adapted to detect acoustic waves, magnetoacoustic waves and magnetic waves, the wave type detected indicating the presence or absence of a circular magnetic domain.

Claim 9

A circular magnetic domain device as claimed in claim 2 wherein the detection means also include concentration means for causing the generated wave to concentrate along at least one path in the said layer between the generating and detection transducers, the said at least one wave concentration path being arranged such that the wave concentration intercepts at least one domain propagation path.

Claim 10

A circular magnetic domain device as claimed in claim 8 wherein the generated waves are magnetic waves and wherein the concentration means consist of a pattern formed in the surface topography of the major surface of the said layer, the said pattern defining at least one path.

Claim 11

A circular magnetic domain device as claimed in claim 8 wherein the generated waves are acoustic waves and wherein the concentration means include a pattern of a material having elastic properties that are dissimilar to the elastic properties of the material of the said layer, the said pattern defining at least one path and being formed on the major surface of the said layer.

Claim 12

A circular magnetic domain device as claimed in claim 10 wherein the pattern is of a material selected from the group which comprises silica, nickel and nickel-iron.